The present invention relates in general to autonomous vehicle control, and, more specifically, to planning and following a post-impact path that reduces risks of secondary crash events.
Several vehicle control systems currently exist which are used to augment the driving capability of a vehicle operator such as antilock brake systems (ABS), traction control systems (TCS), and stability control systems (SC). Examples of stability control systems include electronic stability control (ESC) systems (sometimes referred to as yaw stability control (YSC) systems) and roll stability control (RSC) systems. ESC systems are also sometimes called ESP (Electronic Stability Program) systems or DSTC (Dynamic Stability Traction Control) systems.
The stability control systems are utilized to maintain controlled and stable vehicle operations for improved vehicle and occupant safety. The stability control systems are often used to maintain control of a vehicle following a driver's desired travel direction, to prevent the vehicle from spinning out, and/or to prevent or mitigate a roll over event. For example, a yaw stability control system typically compares the driver's desired heading based upon the steering wheel angle with the path of travel as determined from motion sensors located on the vehicle. By regulating the amount of braking at each corner of the vehicle and the traction force of the vehicle, the desired path of travel may be maintained.
Existing stability control systems correct undesired vehicle motion caused by a tire force disturbance (TFD), such as a tire force differential due to a road surface disturbance or due to a mismatch between the driving intention of a driver and a road surface condition. This mismatch usually happens when there is a significant difference between the front and the rear tire lateral forces applied to the vehicle (referred to as the lateral tire force differential), or there is a significant difference between the right and the left tire longitudinal tire forces (referred to as the longitudinal tire force differential), or a combination thereof.
An undesired yaw motion may also be generated by a yaw moment disturbance caused when a vehicle receives a force disturbance other than a tire force disturbance. A body force disturbance (BFD) may occur when a vehicle hits a fixed object, such as a tree, or when the vehicle is hit by another moving object, such as a vehicle. A body force disturbance may also occur when the vehicle experiences a sudden strong wind gust applied to the vehicle body. While the magnitude of the tire force disturbance is limited by the driving condition of the road surface, the magnitude of a body force disturbance can be essentially unlimited. For example, the collision of two moving vehicles may generate a body force disturbance with a magnitude that is several factors larger than the total tire forces. A yaw motion may be generated when a vehicle receives a body force disturbance from an external source, resulting in an altered vehicle trajectory or path which can result in a secondary impact event. In many situations, the risk of injury or damage can be much greater from a secondary event than from the primary event.
Stability control systems aid a vehicle driver in pursuing an intended action or trajectory. As a result of the impending or actual application of a body force disturbance, however, a driver may panic and perform driving tasks that are inappropriate or drastic in an attempt to avoid receiving the external body force disturbance which can lead to further undesirable events. Some studies have shown that about one third of all vehicle-to-vehicle accidents that cause severe injuries involve more than one impact. A relatively small first impact is very often followed by a severe second impact. This second impact can include one of many types of impacts, such as vehicle-to-vehicle collisions, vehicle-to-object collisions, tripped or untripped roll-overs, and road departures.
It would be desirable to automatically react to impact events while taking into account to possibility of erroneous driver's action in a manner that reduces the likelihood and/or severity of secondary impact events.